This gives me an error message: "The file/directory
epiunwarp/dfield.nrrd does not exist or cannot be read."
I am sure that the file exists, so there must be some kind of
problem reading the file. My operative system is Windows 7. I have
tried the same thing in Cygwin (on the same computer), and there it
works perfectly fine. However, I am going to do the EPI unwarping
in another program (in MeVisLab, using an "External Executable
Wrapper"), and I don't think that can be done via Cygwin.
Therefore, I want this to work using only the Windows command line.

I am very not very familiar with using command line tools. However,
a solution that fixed one of my earlier problems (missing .dll
file) was installing a Visual C++ Redistributable, so I tried
installing all of them, but that didn't help. Or is it possible to
completely omit the problem by having the deformation field in
another file format than .nrrd?